In a communication base station, direct-current power supply with certain level of voltage capacity is commonly applied to various apparatus and equipments in the system. Usually, a conventional base station uses a diesel fuel generator as a backup of the city power supply in a manner of selectively switching between outputs of the city power and the diesel fuel generator and converting the power from alternating-current into direct-current in order to comply with the voltage level required by those communication apparatus. Along with the increasing problems of global energy shortage and popularity of mobile communication application, introducing new clean power supply system becomes more and more desirable. Now many base stations employ hybrid wind-solar power supply system, which uses wind generator and/or solar panels as main equipment for power supply, and uses the diesel fuel generator or the city power as a backup, such that not only the energy consumption of the whole system is reduced, but the reliability for the power supply system is also increased, therefore the communication quality can be secured.
Presently, there are mainly four types of wind-solar complementary power supply systems used in the communication technology. The first type applies a wind-solar complementary power supply system in a communication base station. This type of system converts wind power and solar power into −48V or 24V direct-current electricity and stores the electricity power into battery sets at first, and then supplies the DC electricity power to the communication base station. The second type is consisted of a wind-solar complementary power supply system, multiple inverters and multiple power switches. This type of system converts wind and solar power into direct-current electricity and also saves the electricity power into the battery sets, and then the direct-current is converted into three phase alternating-current through the inverters. The power switches are controllable to switch between two positions, a first one for charging electricity into the battery sets, a second one for supplying power to the system apparatus. The third type includes multiple wind-solar complementary power supply systems in combination with multiple power switches, and in fact, said wind-solar complementary power supply systems and said multiple power switches work independently. In a normal condition, the system is supplied by the wind-solar complementary power supply system, when the wind and solar power is insufficient, the power switch will switch on the city power or a diesel fuel generator so as to connect it with the system to supply power output therefrom. The fourth type is a hybrid wind-solar-diesel power supply system integrated with a power switch model which is managed in a centralized manner. In a normal condition, the system is supplied by the wind-solar complementary power system, which converts the wind power and solar power into direct-current of −48V or 24V. When the wind and solar power is insufficient, the power switch model will switch on the city power or a diesel fuel generator to supply power to the system.
All the above described four types of wind-solar complementary power supply systems have some disadvantages. The first type of system merely applies the wind-solar complementary power supply system for power supply, for the sake of reliability for supplying power to the system in the case of the wind and solar power resource being insufficient for a long time, there must be some battery sets with high capacity, and those battery sets must be fully discharged/charged frequently, so the life of those battery sets must be reduced and the cost of the whole system will also be increased. The second type of system employs multiple inverters for power conversion, which need a set of additional high voltage battery sets, so that the system efficiency is reduced and the cost is increased. In the third type of system, because the multiple wind-solar complementary power supply systems and the multiple power switches are working independently, there must be multiple battery control units existing, which is not advantages to the management of the battery sets, not only the system efficiency is lowered but also the overall system expenses is increased. Moreover, when the power supply systems and the power switches are working concurrently, it is quite difficult to control the charging current which may easily result in overloading of the battery sets and therefore reduce the life of the battery sets. The fourth type of system is only an simple accumulation of the wind-solar power supply system and the power switch model, although the management quality of battery sets is improved, as the system size is too big, its total expense is still high and its efficiency is still low.
Therefore, it is much desirable to develop a new type of hybrid power supply system which is an integration of new clean power supply system with the conventional power supply system, and therefore, much applicable for communication base station.